arXiv subjects

Marcelo Mora

Publications and source records attributed to Marcelo Mora.

5 recordsLinked to original sources

arXiv2025

Colors and Dynamics of a Near-Sun Orbital Asteroid Family: 2021 PH27 and 2025 GN1

We observed the dynamically similar near-Sun asteroids 2021 PH27 and 2025 GN1 for their optical colors. These objects have the lowest known semi-major axes of any asteroids. 2021 PH27 has the largest general relativistic effects of any known solar system object. The small semi-major axis and very close passage to the Sun suggests the extreme thermal and gravitational environment should highly modify these asteroids' surfaces. From g', r', i' and z'-band imaging, we find the colors of 2021 PH27 to be between the two major asteroid types the S and C classes (g'-r'= 0.58 +- 0.02, r'-i'=0.12 +- 0.02 and i'-z'=-0.08 +- 0.05 mags). With a spectral slope of 6.8 +-0.03 percent per 100nm, 2021 PH27 is a X-type asteroid and requires albedo or spectral features to further identify its composition. We find the dynamically similar 2025 GN1 also has very similar colors (g'-r'=0.55 +-0.06 and r'-i'=0.14 +-0.04) as 2021 PH27, suggesting these objects are fragments from a once larger parent asteroid or 2021 PH27 is shedding material. The colors are not blue like some other near-Sun asteroids such as 3200 Phaethon that have been interpreted to be from the loss of reddening substances from the extreme temperatures. There is no evidence of activity or a large amplitude period for 2021 PH27, whereas 2025 GN1 might have a more significant rotational light curve. 2025 GN1 may have a very close encounter or hit Venus in about 2155 years and likely separated from 2021 PH27 in about the last 10 kyrs.

astro-ph.EP↗

arXiv2025

Exploring the stellar streams and satellites around the giant low surface brightness galaxy Malin 1

Giant Low Surface Brightness galaxies (gLSBGs), such as Malin 1, host extended stellar and gaseous discs exceeding $100~\mathrm{kpc}$ in radius. Their formation and evolution remain debated, with satellite interactions and accretion streams proposed as key drivers. Malin 1 exhibits multiple companions and two giant stellar streams extending up to $200~\mathrm{kpc}$. We investigate the orbital dynamics of Malin 1's satellites and their potential connection to these streams. Using optical and HI rotation curve data, we constructed gravitational potentials for Malin 1 incorporating stellar, gaseous, and dark matter components under both Navarro-Frenk-White (NFW) and pseudo-isothermal (ISO) halo profiles. Several scenarios yield bound orbital solutions. The ISO model ($M_{\rm virial} \approx 2.6 \times 10^{12}~M_\odot$) favours bound satellite orbits more than the lower-mass NFW model ($M_{\rm virial} \approx 1.4 \times 10^{12}~M_\odot$). The giant stellar streams could be substructures located along the leading and trailing trajectories of satellite companions. Orbital modeling indicates that the distant satellite eM1 reached pericentre $\sim 1.6~\mathrm{Gyr}$ ago, whereas closer companions interacted as recently as $\sim 100~\mathrm{Myr}$ ago, with one companion currently experiencing strong interaction. Another close companion displays leading/trailing arms in a radial orbit, alongside a polar orbit solution. Unbound solutions linking satellites with streams are also identified. These alignments suggest past interactions shaped Malin 1's morphology, providing new constraints on gLSBG dynamical evolution consistent with recent kinematic studies.

astro-ph.GA↗

arXiv2022

The giant low surface brightness galaxy Malin 1: new constraints for its molecular gas mass from GBT/ARGUS observations

We report on results from GBT/ARGUS $^{12}$CO(1-0) observations for the giant low surface brightness galaxy Malin 1, which allow us to determine an upper limit for its CO mass, and hence its molecular gas mass and molecular gas mass surface density $\Sigma_{H_2}$. Although we performed very deep observations through 17 hours on source integration time, reaching a noise level of $\sim 0.2$ mK (T$^{*}_{A}$) with a corresponding extended source CO limit (3$\sigma$) of 0.09 K km s$^{-1}$, 19 times more sensitive than previous works, we do not detect the $^{12}$CO(1-0) emission line. However, the observations allow us to estimate an upper limit (3$\sigma$) for the CO mass of about $7.4 \times 10^9$ M$_\odot$ for the extended emission, and $1.4 \times 10^8$ M$_\odot$ for the central part of the galaxy. With these figures we conclude that the molecular gas surface density is lower than 0.3 M$_\odot$ pc$^{-2}$, and the corresponding molecular to atomic gas mass ratio is lower than 0.13. The evidence suggests a quite different physical conditions for the interstellar medium in Malin 1 compared to that of normal, high surface brightness spirals. This, in one way to another, keeps an usual molecular gas tracer as CO hidden from our observations, in spite of the diverse stellar and structural properties of Malin 1 observed by several authors since more than 30 years.

astro-ph.GA↗

arXiv2022

BUDDI-MaNGA II: The Star-Formation Histories of Bulges and Discs of S0s

Many processes have been proposed to explain the quenching of star formation in spiral galaxies and their transformation into S0s. These processes affect the bulge and disc in different ways, and so by isolating the bulge and disc spectra, we can look for these characteristic signatures. In this work, we used BUDDI to cleanly extract the spectra of the bulges and discs of 78 S0 galaxies in the MaNGA Survey. We compared the luminosity and mass weighted stellar populations of the bulges and discs, finding that bulges are generally older and more metal rich than their discs. When considering the mass and environment of each galaxy, we found that the galaxy stellar mass plays a more significant role on the formation of the bulges. Bulges in galaxies with masses $\geq10^{10}M_\odot$ built up the majority of their mass rapidly early in their lifetimes, while those in lower mass galaxies formed over more extended timescales and more recently. No clear difference was found in the formation or quenching processes of the discs as a function of galaxy environment. We conclude that more massive S0 galaxies formed through an inside-out scenario, where the bulge formed first and evolved passively while the disc underwent a more extended period of star formation. In lower mass S0s, the bulges and discs either formed together from the same material, or through an outside-in scenario. Our results therefore imply multiple formation mechanisms for S0 galaxies, the pathway of which is chiefly determined by a galaxy's current stellar mass.

astro-ph.GA↗

arXiv2005

Continuous star cluster formation in the spiral NGC 45

We determined ages for 52 star clusters with masses < 10^6 solar masses in the low surface brightness spiral galaxy NGC 45. Four of these candidates are old globular clusters located in the bulge. The remaining ones span a large age range. The cluster ages suggest a continuous star/cluster formation history without evidence for bursts, consistent with the galaxy being located in a relatively unperturbed environment in the outskirts of the Sculptor group.

astro-ph↗